The long-term goal of this laboratory is to employ cell culture to delineate the interactions between vascular endothelial cells and blood-molecular systems, both in health and disease. The more immediate objective of this work, and that to which this proposal is specifically addressed, is to develop an understanding of endothelial cell-mediated fibrinolysis as an approach for investigating the role of the endothelium in thrombolysis. Rabbit and borine vascular endothelial cells cultured in vitro will be employed to characterize the nature of signals which influence the synthesis, secretion, and activity of a recently described cellular plasminogen activator and fibrinolytic inhibitor.